System and method for removing asbestos particles from a slurry

ABSTRACT

A system and method for removing asbestos and other hazardous solids from a slurry collected during removal of insulation from pipelines, equipment and other structures. The slurry is collected in a collection pan that is attached to a shroud of a hydrocleaning machine. Solid particles are separated from the slurry by passing the slurry through various stages of filters. Pumps are used to transfer the slurry from the collection pan through the filter stages. A first flocculent is injected into the slurry to coagulate the solid particles into individual masses. A second flocculent is injected into the slurry, downstream from the injection point of the first flocculent, in order to coagulate a majority of the remaining solid particles. The coagulated masses of solid particles are removed by passing the slurry through a screen shaker. The slurry discharged from the screen shaker is then passed through further filters.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system and method for removing asbestos andother contaminated or hazardous solids from a slurry which is collectedduring removal of insulation from pipelines, equipment and other similarstructures.

2. Description of Prior Art

U.S. Pat. Nos. 5,052,423 and 5,074,323 disclose an apparatus forhydrocleaning the exterior surface of a pipeline or the like. Aplurality of liquid jet nozzles are mounted with respect to a frame soas to surround, during use, the pipeline in circumferentially spacedapart relationship to one another. High-pressure liquid is supplied tothe liquid jet nozzles. The frame travels longitudinally relative to thepipeline to effect cleaning of the pipeline exterior surface.

U.S. Pat. No. 4,809,391 teaches an apparatus for removing contaminantmaterial from a building. The apparatus is a box-shaped device forremoving asbestos from horizontally and vertically arranged pipes. Aplurality of glove apertures are formed in two opposing sidewalls of abox-shaped device. A glove is connected to the sidewall at each apertureand the glove extends into the enclosure. The enclosure operates at anegative pressure. A filter is used at each suction aperture to trapairborne asbestos material.

U.S. Pat. No. 4,723,969 discloses an apparatus and process for removingasbestos and other hazardous material. A vacuum loader is used toremove, collect, seal and dispose asbestos and other hazardous material.The vacuum loader includes a bulk separator compartment, a filteringcompartment downstream of the bulk separator, and a collectorcompartment having a dust settlement chamber.

U.S. Pat. Nos. 4,718,925 and 4,749,391 teach a material collectionreceiver having a bag assembly with a porous or perforated inner bagpositioned within the interior of a solid imperforate bag. A perforatedinner shell is used to accommodate expansion of the bags. A shroudprevents hazardous material from contaminating the outside of the outerbag. A vacuum tank surrounds the shroud.

U.S. Pat. No. 4,897,121 discloses a process for removing asbestos-filledlinings or coatings applied on a surface of a building. U.S. Pat. No.4,002,004 teaches a method for packaging asbestos fibers intoconsolidated blocks.

Other conventional methods for removing and disposing of asbestos andother hazardous material include: wet-bag methods that conform toEnvironmental Protection Agency standards; hand-scraping; hand-heldhigh-pressure waterlances; line travel knife and brush equipment;rotating abrasive wheels; machine blasting with sand or other particles;and line travel high-pressure water jetting equipment. According to thewet-bag methods, asbestos materials are dampened. The dampened pieces ofasbestos and other hazardous material are then removed by hand andplaced into special storage bags.

It is apparent that there exists a need for an automated system andmethod for collecting and separating asbestos and other hazardousmaterials and disposing of such materials within guidelines establishedby the Environmental Protection Agency (EPA), Occupational Safety andHealth Administration (OSHA), or by other governing standards.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a system and method forautomatically removing and separating asbestos and other hazardousmaterial.

It is another object of this invention to provide an automated systemand method for removing solid particles from a slurry by injecting afirst flocculent into the slurry and preferably injecting a secondflocculent into the slurry, downstream from the injection point of thefirst flocculent.

The above-mentioned and other objects of this invention are accomplishedwith a system for removing asbestos and other hazardous solids from aslurry collected during removal of insulation from pipelines, equipmentand other similar structures, wherein the system includes a collectionpan which is attached to a shroud of a hydrocleaning machine. Thehydrocleaning machine uses high-pressure water to blast asbestos andother insulation materials away from a pipeline, equipment, or othersimilar structure. The water and solid particles form a slurry which ispreferably collected within the collection pan.

A first flocculent, preferably an anionic polymer flocculent, isinjected into the slurry. The first flocculent causes formation ofindividual masses of solid particles. The second flocculent, preferablya cationic polymer flocculent, is injected into the slurry downstreamfrom the point of injection of the first flocculent. The secondflocculent causes a majority of individual particles remaining in theslurry, after injection of the first flocculent, to form individualmasses.

After the flocculent injection, the slurry is passed through a screenshaker for separating a first portion of the solid particles anddischarging a first remaining portion of the solid particles with theslurry. The first remaining portion of the slurry is then passed throughan air flotation cell, or other similar filter or separator, forremoving a second portion of the solid particles and discharging asecond remaining portion of the solid particles with the slurry. Thesecond remaining portion of the slurry discharged from the air flotationcell is then passed through at least one cartridge filter, bag filter orother fine particulate filter. The water discharged from the cartridgefilter or other suitable filter preferably meets required emissionsstandards, such as Resource Conservation and Recovery Act (RCRA), OSHA,EPA and/or other governing standards.

In one preferred embodiment according to this invention, at least aportion of the water discharged from the cartridge filter or othersuitable filter is recycled back to the shroud of the hydrocleaningmachine. Such recycled water is preferably used to rinse the pipelineafter the hydrocleaning machine has stripped the pipeline. The recycledwater can also be used to fluidize the solid particles and thus form theslurry. It is apparent that the recycled water can be sent eitherdirectly to the shroud and/or the collection pan of the hydrocleaningmachine or directly to the fresh water tank.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features of this invention will becomemore apparent when viewed in conjunction with the drawings wherein:

FIG. 1 is a process flow diagram showing a method and system arrangementfor separating asbestos particles and other hazardous or undesirablesolid particles, according to one preferred embodiment of thisinvention;

FIG. 2 is a diagrammatic flow diagram showing a method and systemarrangement similar to that shown in FIG. 1;

FIG. 3 is a diagrammatic perspective view of a gimbal device that canaccommodate a screen shaker, according to one preferred embodiment ofthis invention;

FIG. 4 is a detailed front view of a screen shaker mounted in a gimbaldevice, similar to the gimbal device shown in FIG. 3;

FIG. 5 is a detailed side view of the screen shaker mounted in thegimbal device, as shown in FIG. 4;

FIG. 6 is a front view of a gimbal device mounted on a disposalcontainer, that accommodates a disposable bladder bag, according toanother preferred embodiment of this invention;

FIG. 7 is a side view of the mounted gimbal device, as shown in FIG. 6;

FIG. 8 is a plan view of a system train according to one preferredembodiment of this invention;

FIG. 9 is a plan view of a system train according to another preferredembodiment of this invention;

FIG. 10 is a front view of the system train shown in FIG. 9;

FIG. 11 is a front view of a slinger apparatus, according to onepreferred embodiment of this invention;

FIG. 12 is a side view of the slinger apparatus shown in FIG. 11; and

FIG. 13 is an end view of the slinger apparatus shown in FIG. 11.

DESCRIPTION OF PREFERRED EMBODIMENTS

U.S. Pat. Nos. 5,052,423 and 5,074,323 teach a process and apparatus forhydrocleaning the exterior surface of a pipeline to remove coatings,particularly coatings containing asbestos materials. The teachings ofsuchreferences are incorporated into this specification by referencethereto. As shown in FIG. 2, hydrocleaning machine 11 is preferably anapparatus similar to the hydrocleaning apparatuses taught by U.S. Pat.Nos. 5,052,423 and 5,074,323. However, it is apparent that the systemand method of this invention can be used with other conventionalapparatuses for removing insulation and other coatings from a pipeline,a piece of equipment, or another structure. Generally speaking, thisinvention relates to a system and method for collecting, separating andfiltering asbestos particles and other hazardous or undesirable solidparticles within a slurry which is generated from conventionalapparatuses or methods for removing such solids.

Collection means are used to collect a slurry resulting from thehydrocleaning process. Typically, such slurry contains asbestos andpossibly other hazardous or undesirable solids. According to onepreferredembodiment of this invention, the collection means comprisecollection pan 16 which is preferably attached to shroud 15 ofhydrocleaning machine 11. The collection means may also comprise aparticle shredder, not shown in the drawings, which is preferablymounted within a lower portion of collection pan 16. The particleshredder comprises rotating fingers that pass between stationary membersattached to the shredder walls. The particle shredder preferably sheersall large solid particles to a given size, such as a size no larger thanapproximately one-half inch. It is apparent that the collection meansmay comprise any other suitable device for collecting and/or storingsuch slurry.

Separation means are used to separate solid particles from the slurry.Suchsolid particles typically include asbestos and may also includeother hazardous solid particles. In one preferred embodiment accordingto this invention, the separation means comprise first filtration meansfor separating or filtering a first portion of the solid particles andfor discharging a first remaining portion of the solid particles withthe slurry. As shown in FIGS. 1, 2, 4 and 5 and according to onepreferred embodiment of this invention, the first filtration meanscomprise screen shaker 70. It is apparent that any other suitableseparation device can beused. However, the screen shaker is effectiveand relatively economical forremoving large masses of the solidparticles.

FIGS. 3, 6 and 7 show various embodiments of a gimbal device upon whichscreen shaker 70 can be mounted, according to this invention. As shownin FIG. 3, screen shaker support 71 is attached to frame 72. Gimbalbearings 74 are used to rotatably attach frame 72 with respect to frame73. Crossbar 76 is secured to crossbar 77 in any suitable manner knownto those skilled in the art. Gimbal bearings 75 are used to rotatablyattach crossbar 77 with respect to frame 73.

FIGS. 4 and 5 show screen shaker 70 mounted within a gimbal devicesimilar to those shown in FIGS. 6 and 7. As shown in FIG. 5, screen 78is attachedor mounted within the housing of screen shaker 70. Screen 78is preferably mounted at an incline so that the sludge and other solidscan flow or travel through discharge 79.

As shown in FIGS. 6 and 7, the gimbal device that accommodates screenshaker 70 is mounted to container 66. Container 66 is preferably mountedon a transportable skid that is transported by a train, as discussedlaterin this specification. Because of the various terrains upon whichthe transportable skid is transported, frame 73 is often positioned atvariousangles with respect to the ground, as the gimbal device andscreen shaker 70 are transported. The overall result of the gimbaldevice and screen shaker 70, as shown in FIGS. 3-7, is that screenshaker 70 remains level with respect to the ground and gravitationalforces. Thus, as frame 73 moves at various angles with respect to theground and gravity, screen shaker 70 will remain level so that thesludge material does not slide or shift to any one particular side ofscreen shaker 70, due to gravitationalforces. As shown in FIGS. 6 and 7,lockup mechanism 80 is used to prevent unwanted shifting of the gimbaldevice, for example, as the transportable skid is started or moved froma zero-acceleration condition.

Screen shaker 70 is vibrated so that a shaking action is imparted toeitherthe housing of screen shaker 70 or frame 73 and thus screen 78. Itis apparent that frame 73 and/or screen 78 can be mechanically vibratedby any suitable vibration means known to those skilled in the art. Thevibration means are preferably housed within the lower portion of thehousing of screen shaker 70.

As shown in FIG. 2, shroud 15 preferably operates at a slight vacuumpressure in order to prevent undesirable solid particles fromdischarging outside of shroud 15. Vacuum pump 14 maintains a negativepressure within shroud 15. Vacuum pump 14 is preferably a HEPA vacuumpump which is typically rated with a minimum efficiency of 99.99% at 0.3microns, D.O.P.method, such as those available commercially from acompany named Pullman/Holt. Fresh water tank 12 is preferably used tosupply water to high-pressure fresh water pump 13, which is upstream ofhydrocleaning machine 11.

Transfer pump 17 is used to move the slurry from collection pan 16 toscreen shaker 70 or another suitable first filtration means. Transferpump17 discharges into slurry conduit 22 which discharges to screenshaker 70. Transfer pump 17 is preferably an impeller pump with anautomatic air ejector priming device but could also be a peristaltichose pump or another suitable pump known to those skilled in the art.Transfer pump 17 is preferably the same as or similar to a ModelDP21-76PB pump which is commercially available from Godwin Pumps ofAmerica, Inc. of Bridgeport, N.J.

Flocculent injection means are used to inject a first flocculent intothe slurry and to preferably inject a second flocculent into the slurry,downstream from the injection point of the first flocculent. As shown inFIGS. 1 and 2, injection pump 25 is used toinject the first flocculentinto the slurry. Injection pump 25 discharges through injection conduit26and into shroud 15. Check valve 27 is preferably installed withininjectionconduit 26. The first flocculent is preferably injected intoshroud 15 so that individual masses of the solid particles begin to formin the slurry within shroud 15. However, it is apparent that the firstflocculent can beinjected at other points within the slurry flow.

The flocculent injection means may also comprise injection pump 30 whichdischarges a second flocculent through injection conduit 31 and checkvalve 32 and then into the slurry, preferably upstream of screen shaker70or another suitable first filtration means. It is apparent that onlythe first flocculent must be injected into the slurry to accomplish theobjective of this invention; however, injecting a second flocculent isadvantageous since it significantly reduces the need for filter changesdownstream from screen shaker 70. Injection pumps 25 and 30 are eachpreferably a PolyBlend® automated polymer feed system, commerciallyavailable from Stranco, Inc. of Bradley, Ill., or other similar pump orfeed system. It is apparent that either injection pump 25 or 30 can bereplaced with other suitable means apparent to those skilled in the artfor introducing the flocculent into the slurry stream.

According to another preferred embodiment of this invention, theseparationmeans further comprise second filtration means for separatinga second portion of the solid particles and for discharging a secondremaining portion of the solid particles with the slurry. As shown inFIGS. 1 and 2,the second filtration means comprise air flotation cell35. It is apparent that other suitable and conventional filters and/orseparators can be usedin lieu of the air flotation cell. However, airflotation cell 35 is provenas an effective second filtration means. Onepreferred and suitable air flotation cell is commercially available fromANDERSONICS, of Bakersfield,Calif. In such air flotation cell, theinfluent is directed tangentially into a center well. A centrifugeaction promotes migration of droplets to the center of the apparatus.Water migrates to a stilling area of the apparatus. The migrated cleanwater is drawn off by a suction pump. Such suction pump provides motiveforce for gas induction and enough head to transfer the clean fluidsfrom the apparatus. The high pressure is forced back into the vessel toinduce the gas and air which is pulled off of a gas cap at the top ofthe apparatus. The asbestos and other hazardous or undesirable solidparticles attach to the bubbles and are lifted to a skimtrough. The skimproduced is then discharged as sludge to surge tank 60, asshown FIG. 2.As shown in FIG. 2, a slurry from surge tank 60 is recycled back toscreen shaker 70, or another suitable first filtration means, and thesludge is discharged from surge tank 60 to bladder 65. Bladder 65alsoaccepts solids discharged through solids discharge conduit 21 fromscreen shaker 70. Bladder 65 is preferably mounted within container 66,which is shown in FIGS. 6 and 7.

FIGS. 11-13 show one preferred embodiment of slinger 40, according tothis invention. Slinger 40 is used to evenly distribute the sludgematerial that is deposited into bladder 65, or any other suitablecontainer. Because the sludge product according to this invention hassuch a lower water content, the deposited sludge tends to pile withoutcompletely filling bladder 65 or another suitable container. Slinger 40is used to evenly distribute the separated-out solid particles or sludgematerial so that bladder 65 or another suitable container can becompletely filled, rather than only partially filled.

According to one preferred embodiment of this invention, slinger 40 issecured with respect to frame 73 by any suitable means known to thoseskilled in the art. A flexible hose or conduit is preferably positionedbetween discharge 79 and passage 42 of slinger 40. The solids which areseparated from the slurry by screen shaker 70 are routed through passage42 and fall onto slinger plate 41. Slinger plate 41 rotates at asuitable speed and thus evenly distributes the solids completely withinbladder 65.

In another preferred embodiment according to this invention, theseparationmeans further comprise third filtration means for separating athird portion of the solid particles and for discharging a thirdremaining portion of the solid particles with the slurry. The thirdfiltration meansmay comprise one or more cartridge filters 50 forremoving enough of the solid particles from the third remaining portionof the slurry to meet required emissions standards, such as those set byRCRA, OSHA, EPA and/or other governing bodies. FIG. 2 shows twodifferent arrangements for cartridge filter 50, either or both of whichcan be used in the system. The third remaining portion of the slurrywhich is discharged by slurry pump 36 from the discharge of airflotation cell 35 flows through slurry conduit 37 to at least onepreferred cartridge filter 50.

As shown in FIG. 2, each cartridge filter 50 can be blocked andbypassed. Cartridge filter 50 may be an in-line separator, such as anIL-B/S in-lineseparator which is commercially available from ClaudeLaval Corporation of Fresno, Calif. However, it is also apparent thatother suitable bag filters or suitable fine particulate filters can beused in lieu of or in conjunction with the cartridge filter.

At least a portion of the separated slurry discharged from cartridgefilter50 can be recirculated back to fresh water tank 12 or to shroud 15of hydrocleaning machine 11. Recirculation means are used to recycle theseparated slurry. According to one preferred embodiment to thisinvention,the recirculation means comprise recirculation pump 55 andrecirculation conduit 56. However, it is apparent that other suitablefluid transfer apparatuses can be used to recirculate or recycle theseparated slurry. The water discharged from cartridge filter 50 whichmeets the required emissions standards may also be discharged to ground.

Transfer means are used to transfer the slurry throughout the system. Asshown FIGS. 1 and 2, the transfer means comprise transfer pump 17 andslurry pump 36. However, it is apparent that other suitable positivepressure pumps and/or vacuum pumps can be positioned throughout thesystemto accomplish the slurry transfer.

FIGS. 8-10 show various arrangements of a system train according to thisinvention, the system elements are preferably mounted on transportableskids. As shown in FIG. 8, fresh water tank 12 moves with a sideboomtractor or the like and the remaining system train moves in an axialdirection, with respect to the pipeline. The sideboom tractor cradlesthe pipeline and hydrocleaning machine 11 propels itself, according toone preferred embodiment of this invention.

According to another preferred embodiment of this invention, the methodforremoving asbestos particles and other hazardous or undesirable solidparticles from a slurry collected during removal of insulation frompipelines, equipment or other structures, begins with transferring theslurry from the collection means to the separation means. At least aportion of the solid particles are separated from the slurry byinjecting a first flocculent into the slurry. More solid particles canbe separated from the slurry by injecting a second flocculent into theslurry, downstream from the injection point of the first flocculent. Thefirst flocculent preferably is an anionic (emulsion) polymer flocculent,such asa flocculent which is commercially available and known asJAYFLOC™ 803, from Exxon Chemical Company. Such flocculent is effectivein forming individual masses of approximately 80-90% of the solidparticles. The anionic polymer flocculent has a net negative charge.

One preferred type of the second flocculent is JAYFLOC™ 838 LiquidCationic Polyelectrolyte, a cationic (solution) polymer commerciallyavailable from Exxon Chemical Company, which is a coagulant with a highmolecular weight and a very high charge density. The cationic polymerflocculent has a net positive charge and thus coagulates a majority oftheremaining solid particles to form individual masses that tend tocoagulate with the individual masses of solid particles formed by thefirst anionic polymer flocculent.

All individual masses of solid particles are passed with the slurrythroughscreen shaker 70. The second flocculent is preferably injectedinto the slurry between the collection means and the separation means.

The method of this invention also includes transferring the slurrythrough the filtration means and the other elements of the system, aspreviously discussed in this specification, until the effluent meetsrequired environmental emission and/or other safety standards. Asindicated in FIG.2, samples of the water or the slurry can be takenthroughout various points within the system. The water or slurry qualitycan be determined atsuch various sample points within the system and thevalves can be used to control the system and thus vary the qualities ofthe water or slurry.

While in the foregoing specification this invention has been describedin relation to certain preferred embodiments thereof, and many detailshave been set forth for purpose of illustration it will be apparent tothose skilled in the art that the invention is susceptible to additionalembodiments and that certain of the details described herein can bevariedconsiderably without departing from the basic principles of theinvention.

We claim:
 1. A method for removing asbestos and other hazardous solidparticles from a slurry collected during removal of insulation frompipelines, equipment or other structures, the method including:(a)transferring the slurry from collection means to separation means; (b)injecting a first flocculent into the slurry and injecting a secondflocculent into the slurry downstream from the injection of the firstflocculent; and (c) separating a first portion of solid particles fromthe slurry in a first separation means thereby forming a first remainingslurry containing solid particles, and (d) separating a second portionof solid particles from said first remaining slurry to form a secondremaining slurry containing solid particles, and (e) separating a thirdportion of solid particles from said second remaining slurry to formwater recyclable to said process of removing insulation from pipelines,equipment or other structures.
 2. A method according to claim 1 whereinthe slurry is collected in a collection pan attached to a shroud of ahydrocleaning machine.
 3. A method according to claim 1 wherein theslurry is passed through a particle shredder within a shroud of ahydrocleaning machine.
 4. A method according to claim 1 wherein thefirst portion of the solid particles is separated by passing the slurrythrough a screen shaker.
 5. A method according to claim 1 wherein thesecond portion of the solid particles is removed by passing the firstremaining slurry through an air flotation cell.
 6. A method according toclaim 1 wherein the third portion of the solid particles is removed bypassing the second remaining slurry through at least one cartridgefilter.
 7. A method according to claim 1 wherein the third portion ofthe solid particles is removed by passing the second remaining slurrythrough at least one bag filter.
 8. A method according to claim 1wherein the second remaining slurry is filtered to remove enough of thesolid particles to meet required emission standards.
 9. A methodaccording to claim 1 wherein:the first flocculent is injected into theslurry by introducing the first flocculent into collection means forcollecting the slurry, and said second flocculent is injected into theslurry before separating the first portion of the solid particles fromthe slurry.